I have recently purchased a STF-8300 kit with FW8 and OAG 8300/ST-i. Initially I got shadows on my STF-8300 images but I managed to get rid of them after adjustment of the pickoff mirror (prism). However, the image from the guide camera (ST-i) has almost 1/3 covered with a shadow no matter I adjusted the prism. This shadow does not rotate even if I rotate the connection of STF-8300 to the scope so I suppose it has something to do with the OAG setup. Attached is an image from ST-i attaching to the OAG in daytime showing the shadow on the left side. This shadow would rotate if I rotate the ST-i but still occupies a large area. Please let me know if there is normal or anything else I should try to adjust.